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Friday, April 24, 2009

Can evolution explain how minds work?

....biologists have tended to assume that species with shared ancestry will have similar cognitive abilities, and that the evolutionary history of traits can be used to reveal how we and other animals perform certain mental tasks. A closer analysis suggests things aren't so simple.

...Over the past two decades, researchers have reported that chimpanzees can empathize with other members of their species, and that they reconcile and even console each other after conflicts. Monkeys and apes have been credited with a sense of fairness and aversion to inequity and, in the case of apes, an awareness of the mental states of others — in other words, a theory of mind. A closer look at many of these studies reveals, however, that appropriate control conditions have often been lacking, and simpler explanations overlooked in a flurry of anthropomorphic overinterpretation. For instance, capuchin monkeys were thought to have a sense of fairness because they reject a slice of cucumber if they see another monkey in an adjacent cage, performing the same task, rewarded with a more-sought-after grape. Researchers interpreted a monkey's refusal to eat the cucumber as evidence of 'inequity aversion' prompted by seeing another monkey being more generously rewarded. Yet, closer analysis has revealed that a monkey will still refuse cucumber when a grape is placed in a nearby empty cage. This suggests that the monkeys simply reject lesser rewards when better ones are available.

...Laboratory studies of a number of species performing a wide range of tasks indicate that different species may have arrived at similar solutions to cognitive problems because they have experienced similar selection pressures, not because they are closely related. In other words, evolutionary convergence may be more important than common descent in accounting for similar cognitive outcomes in different animal groups.

...For example, we now know that birds are capable of feats that match or even exceed those reported in monkeys and apes. Rooks, for example, rub their bills together after one of them has been involved in a confrontation with another bird. Equivalent stroking and embracing in chimpanzees would be labelled 'consolation'. The self-directed pecking that magpies show when they are put in front of a mirror after a mark has been placed on their body is similar to the reactions seen in apes given the same treatment. In magpies, this behaviour has been interpreted as evidence for some degree of self-recognition. But in apes, the same behaviour has been thought to indicate a deeper level of self-consciousness. Caledonian crows outperform monkeys in their ability to retrieve food from a trap tube — from which food can be accessed only at one end. The crows can also work out how to use one tool to obtain a second with which they can retrieve food, a skill that monkeys and apes struggle to master.

...Researchers have tried for decades to teach apes some form of language, be it by using visual symbols or gestures. But linguists generally agree that the resulting efforts made by chimps and bonobos don't qualify as language. One of the prerequisites for language is being able to imitate sounds that are created by someone else. Our primate cousins show no inclination to do this. Yet many parrots and songbirds are striking vocal mimics. Furthermore, the way that they learn to sing is not unlike how human infants learn to speak. Both children and the chicks of parrots and songbirds learn many of their vocalizations during a sensitive period early in life. They also undergo a transitional period during which their attempts to speak or sing increasingly come to resemble those of adults. Recent studies even suggest that starlings can identify certain syntactic features of sound patterns that non-human primates miss.

The appearance of similar abilities in distantly related species, but not necessarily in closely related ones, illustrates that cognitive traits cannot be neatly arranged on an evolutionary scale of relatedness.